Dirty butts/ odd shaped eyes

Please forgive me, I am on a very old computer that cannot seem to complete a google search to save my life. My hens have dirty butts and it looks like their eyes have changed from round to almond shape (not the pupils, the physical eyelid) does anyone know off the top of their heads what this is? I know I've read the symptoms before but, of course, I do not have my chicken books on hand either. Thanks!

Please forgive me, I am on a very old computer that cannot seem to complete a google search to save my life. My hens have dirty butts and it looks like their eyes have changed from round to almond shape (not the pupils, the physical eyelid) does anyone know off the top of their heads what this is? I know I've read the symptoms before but, of course, I do not have my chicken books on hand either. Thanks!

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Sorry, I mis-read... I have no idea what it might be. If it were the pupil, I would say Marek's.

Yeah- the pupils are normal and the hens are not blind... I'll have to look up pasty butt, as these are adult hens with access to fresh water 24/7/365. I have never fed my adults a medicated food. I really thought I had read the almond shaped eyes as a symptom to something other than ammonia poisoning. Huh. Thanks for the input!